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    SubjectRe: Writeout in recent kernels/VMs poor compared to last -ac
    Date
    ----- Original Message -----
    From: "Andrea Arcangeli" <andrea@suse.de>
    To: "Adam Kropelin" <akropel1@rochester.rr.com>
    Cc: <linux-kernel@vger.kernel.org>
    Sent: Saturday, January 12, 2002 11:30 AM
    Subject: Re: Writeout in recent kernels/VMs poor compared to last -ac


    > On Sat, Jan 12, 2002 at 10:17:39AM -0500, Adam Kropelin wrote:
    > > I recently began regularly transferring large (600 MB+) files to my
    > > Linux-based fileserver and have noticed what I would characterize as poor
    > > writeout behavior under this load. I've done a bit of comparison testing
    > > which may help reveal the problem better.

    <snip>

    > I think you simply want to trigger the soft-bdflush event earlier, with
    > -aa something like this may do the trick:
    >
    > echo 5 500 64 256 500 3000 60 2 0 > /proc/sys/vm/bdflush
    >
    > this way you'll wakeup as soon as 5% of the 118mbytes (+ free memory,
    > none in this case) are dirty, and bdflush will stop as soon as the level
    > is back to 2% (then kupdate will take care of the 2%). Those suggested
    > values may be too strict but this way you should get the idea if it
    > helps somehow or not :)

    Thanks for the idea. Unfortunately, it didn't help. :(

    Blocks definitely do begin hitting the disk much sooner after I begin the
    transfer, but the overall time is basically unchanged: 7:08. vmstat still shows
    the widely oscillating bo value.

    --Adam


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